Bringing in a new litterbox at the same time as moving the location may have made it difficult for him. It's not uncommon for rabbits to pee over the edge of their boxes when they get a bit big for them. Let him use the new box in the old location for a while, that way it will get his smell etc on it. Then do what you suggested and slowly start to move it across to the new location, maybe an inch every day or every other day. You'll soon find out if you're moving it too fast if he stops using it and poops in the old spot again.
That being said, bunnies are creatures of habit and there's a chance that you may not be able to train him to go in the new spot since they like to go where they like to go.
I'll agree with these statements. All my rabbits (3) have been girls and they lift their back ends up before peeing. Just last week, one of the baby bunnies (big baby bunny) jumped up on our couch and as I was looking at her, I could see her back end lift up...I pointed at her and said NO...She was looking at me ...she peed about a table spoon and jumped off the couch..I think she did this for mischievousness...No harm done since the couch is leather...just wiped it up. Yes, my girl rabbits ocassionally stand up before peeing and pee outside the litter box.
About litter boxes. Just starting out with rabbits in the house...
you must put the litter boxes where they want them. Our previous Bunny, started out with multiple litter boxes in the house. By the time she died a little short of 12 years old she only had one litter box in the entire house...only one litter box for so many years. Our current Flemmish babies, are in a similar phase where they have multiple litter boxes.....three distributed throughout the house. They produce copious amounts of pee in the boxes. They will mark ocassionally mark with pee outside the boxes....just like our previous rabbit, Bunny. She was an adult and stopped this marking thing about 4 to 6 weeks after being turned loose in the house. I'm thinking present baby bunnies will stop this marking thing ....and if they don't, when they are neutered, I'm pretty sure it will stop. Just to repeat myself, with all the rabbits, it wasn't that much of a problem with all hardwood floors and leather furniture. Bunny caused a lot of problems, where she would jump on on our bed and mark our pillows with pee...then we'd have to launder the bed covers!!!
Anyhow, after some teething pains with Bunny, we ended up with a perfect house pet...work with your bunny and you'll have a really nice bunny pet. ..Now...about the Flemmish babies!!!!!We're still working with them. When got Bunny, she was an adult. But now, we're working with baby bunnies in the house!! And of course, these baby Flemmish are already the size of normal rabbits...they are not even 4 months old and they have so much energy and SO much appetite!!!. Bottom line, even near 4 months of age, they are basically very good at litter box training. I think like our previous rabbit, Bunny, when they get the house sufficiently marked (!) and for sure when neutered, their marking pee events will end.
I feel sorry for people that don't have a rabbit to share their house with. They are really lovely clean obedient little animals. You can't really know what nice little and intelligent animals they are until they bond with you.